In fabric coverings, threads of animal hair have been used for a long time for such reinforcement threads. Attempts have already been made to replace such natural threads by synthetic monofilament threads which have wiriness and strength close to those of natural hair. However, the use of such synthetic fibres remains limited for the threads thus obtained tend to slip inside the structure of the fabrics.
To prevent such slipping, it has already been proposed to coat the fabric after the weaving or knitting operation with a bending agent, for example with acrylic resins. This method avoids the above slipping but makes the textile rigid since, following coating with the bonding agent, the threads are all connected together at their contact point. This method does not then make it possible to obtain textiles which, while having the desired wiriness and strength, maintain good flexibility and good resilience.
It has also been envisaged to twist two threads of the same length together, for example a monofilament thread and a hairy thread. The rough surface of the hairy thread ensures the non-slip of the composite thread (FR-A-2 270 355). Such a method cannot be used with threads having great rigidity which would remain rectilinear during a twisting attempt.